Most probable mode list generation scheme

ABSTRACT

A method of signaling an intra prediction mode used to encode a current block in an encoded video bitstream using at least one processor includes determining a plurality of candidate intra prediction modes; generating a most probable mode (MPM) list using the plurality of candidate intra prediction modes; signaling a reference line index indicating a reference line used to encode the current block from among a plurality of reference lines including an adjacent reference line and a plurality of non-adjacent reference lines; and signaling an intra mode index indicating the intra prediction mode, wherein the MPM list is generated based on the reference line used to encode the current block and whether an intra sub-partition (ISP) mode is enabled.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.16/529,941, filed on Aug. 2, 2019, in the United States Patent &Trademark Office, which claims priority from 35 U.S.C. § 119 to U.S.Provisional Application No. 62/791,858, filed on Jan. 13, 2019, in theUnited States Patent & Trademark Office, the disclosures of which areincorporated herein by reference in their entireties.

FIELD

The present disclosure is directed to advanced video codingtechnologies. More specifically, the present disclosure is directed tosimplified most probable modes (MPMs) list generation scheme for zeroline and non-zero lines.

BACKGROUND

ITU-T VCEG (Q6/16) and ISO/IEC MPEG (JTC 1/SC 29/WG 11) published theH.265/HEVC (High Efficiency Video Coding) standard in 2013 (version 1)2014 (version 2) 2015 (version 3) and 2016 (version 4) [1]. In 2015,these two standard organizations jointly formed the JVET (Joint VideoExploration Team) to explore the potential of developing the next videocoding standard beyond HEVC In October 2017, they issued the Joint Callfor Proposals on Video Compression with Capability beyond HEVC (CfP). ByFeb. 15, 2018, total 22 CfP responses on standard dynamic range (SDR),12 CfP responses on high dynamic range (HDR), and 12 CfP responses on360 video categories were submitted, respectively. In April 2018, allreceived CfP responses were evaluated in the 122 MPEG/10th JVET meeting.As a result of this meeting, JVET formally launched the standardizationprocess of next-generation video coding beyond HEVC. The new standardwas named Versatile Video Coding (VVC), and JVET was renamed as JointVideo Expert Team.

The intra prediction modes used in HEVC are illustrated in FIG. 1. InHEVC, there are total 35 intra prediction modes, among which mode 10 ishorizontal mode, mode 26 is vertical mode, and mode 2, mode 18 and mode34 are diagonal modes. The intra prediction modes are signalled by threemost probable modes (MPMs) and 32 remaining modes.

To code an intra mode, a most probable mode (MPM) list of size 3 isbuilt based on the intra modes of the neighboring blocks. this MPM listwill be referred to as the MPM list or primary MPM list. If intra modeis not from the MPM list, a flag is signalled to indicate whether intramode belongs to the selected modes.

An example of the MPM list generation process for HEVC is shown isfollows:

● If (leftIntraDir == aboveIntraDir && leftIntraDir > DC_IDX) ○ MPM [0]= leftIntraDir; ○ MPM [1] = ((leftIntraDir + offset) % mod) + 2; ○ MPM[2] = ((leftIntraDir − 1) % mod) + 2; ● Else if (leftIntraDir ==aboveIntraDir) ○ MPM [0] = PLANAR_IDX; ○ MPM [1] = DC_IDX; ○ MPM [2] =VER_IDX; ● Else if (leftIntraDir != aboveIntraDir) ○ MPM [0] =leftIntraDir; ○ MPM [1] = aboveIntraDir; ○ If (leftIntraDir > 0 &&aboveIntraDir > 0) ▪ MPM [2] = PLANAR_IDX; ○ Else ▪ MPM [2] =(leftIntraDir + aboveIntraDir) < 2 ? VER_IDX : DC_IDX;

Here, leftIntraDir is used to indicate the mode in left block andaboveIntraDir is used to indicate the mode in the above block. If leftor block is currently not available, leftIntraDir or aboveIntraDir willbe to DC_IDX. In addition, variable “offset” and “mod” are the constantvalues, which are set to 29 and 32 respectively.

SUMMARY

In an embodiment, there is provided a method of signaling an intraprediction mode used to encode a current block in an encoded videobitstream using at least one processor, the method including determininga plurality of candidate intra prediction modes; generating a mostprobable mode (MPM) list using the plurality of candidate intraprediction modes; signaling a reference line index indicating areference line used to encode the current block from among a pluralityof reference lines including an adjacent reference line and a pluralityof non-adjacent reference lines; and signaling an intra mode indexindicating the intra prediction mode, wherein the MPM list is generatedbased on the reference line used to encode the current block and whetheran intra sub-partition (ISP) mode is enabled.

In an embodiment, there is provided a device for signaling an intraprediction mode used to encode a current block in an encoded videobitstream, including at least one memory configured to store programcode; and at least one processor configured to read the program code andoperate as instructed by the program code, the program code includingdetermining code configured to cause the at least one processor todetermine a plurality of candidate intra prediction modes; generatingcode configured to cause the at least one processor to generate a mostprobable mode (MPM) list using the plurality of candidate intraprediction modes; first signaling code configured to cause the at leastone processor to signal a reference line index indicating a referenceline used to encode the current block from among a plurality ofreference lines including an adjacent reference line and a plurality ofnon-adjacent reference lines; and second signaling code configured tocause the at least one processor to signal an intra mode indexindicating the intra prediction mode, wherein the MPM list is generatedbased on the reference line used to encode the current block and whetheran intra sub-partition (ISP) mode is enabled.

In an embodiment, there is provided a non-transitory computer-readablemedium storing instructions, the instructions including one or moreinstructions that, when executed by one or more processors of a devicefor signaling an intra prediction mode used to encode a current block inan encoded video bitstream, cause the one or more processors todetermine a plurality of candidate intra prediction modes; generate amost probable mode (MPM) list using the plurality of candidate intraprediction modes; signal a reference line index indicating a referenceline used to encode the current block from among a plurality ofreference lines including an adjacent reference line and a plurality ofnon-adjacent reference lines; and signal an intra mode index indicatingthe intra prediction mode, wherein the MPM list is generated based onthe reference line used to encode the current block and whether an intrasub-partition (ISP) mode is enabled

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, the nature, and various advantages of the disclosedsubject matter will be more apparent from the following detaileddescription and the accompanying drawings in which:

FIG. 1 is a diagram of an example of intra prediction modes in HEVC.

FIG. 2 is a diagram showing an example of reference lines adjacent to acoding block unit.

FIG. 3 is a diagram of an example of intra prediction modes in VVC.

FIG. 4 is a diagram of an example of positions of neighboring CUs.

FIG. 5 is a diagram of an example of division of 4×8 and 8×4 blocks inan Intra Sub-Partitions (ISP) coding mode.

FIG. 6 is a diagram of an example of division of all blocks except 4×8,8×4 and 4×4 blocks in an ISP coding mode.

FIG. 7 is a simplified block diagram of a communication system accordingto an embodiment.

FIG. 8 is a diagram of the placement of a video encoder and decoder in astreaming environment according to an embodiment.

FIG. 9 is a functional block diagram of a video decoder according to anembodiment.

FIG. 10 is a functional block diagram of a video encoder according to anembodiment.

FIG. 11 is a flowchart of an example process for signaling an intraprediction mode used to encode a current block in an encoded videobitstream according to an embodiment.

FIG. 12 is a diagram of a computer system according to an embodiment.

DETAILED DESCRIPTION

Multi-line intra prediction was proposed to use more reference lines forintra prediction, and encoder decides and signals which reference lineis used to generate the intra predictor. The reference line index issignaled before intra prediction modes, and only the most probable modesare allowed in case a nonzero reference line index is signaled. In FIG.2, an example of 4 reference lines is depicted, where each referenceline is composed of six segments, i.e., Segment A to F, together withthe top-left reference sample. In addition, Segment A and F are paddedwith the closest samples from Segment B and E, respectively.

In VVC, there may be a total 95 intra prediction modes as shown in FIG.3, where mode 18 is horizontal mode, mode 50 is vertical mode, and mode2, mode 34 and mode 66 are diagonal modes. Modes −1 through −14 andModes 67 through 80 are called Wide-Angle Intra Prediction (WAIP) modes.

In VTM3.0, the size of MPM list is set equal to 6 for both the adjacentreference line (also referred to zero reference line) and non-adjacentreference lines (also referred to non-zero reference lines). Thepositions of neighboring modes used to derive 6 MPM candidates are alsothe same for adjacent and non-adjacent reference lines, which isillustrated in FIG. 4. In FIG. 4, the block A denotes the leftneighboring coding unit of the current coding unit, block B denotes theabove neighboring coding unit of current coding unit, and variablescandIntraPredModeA and candIntraPredModeB indicate the associated intraprediction modes of block A and B respectively. candIntraPredModeA andcandIntraPredModeB are initially set equal to INTRA_PLANAR. If block A(or B) is marked as available, candIntraPredModeA (orcandIntraPredModeB) is set equal to the actual intra prediction mode ofblock A (or B).

MPM candidate derivation process is different for adjacent andnon-adjacent reference lines. For zero reference line, if both twoneighboring modes are Planar or DC mode, default modes are used toconstruct the MPM list, 2 of them are Planar and DC modes, and theremaining 4 modes are angular modes, which may also be referred to asangular default modes. For non-zero reference lines, if both twoneighboring modes are Planar or DC mode, 6 angular default modes areused to construct the MPM list.

An example of an MPM list derivation process is shown below, whereincandModeList[x] with x=0, 1, 2, 3, 4, 5 denotes the 6 MPM candidates. Inother words, candModeList[0] may denote a 0*MIPM candidate,candModeList[1] may denote a 1 MPM candidate, candModeList[2] may denotea 2^(nd) MPM candidate, candModeList[3] may denote a 3^(rd) MPMcandidate, candModeList[4] may denote a 4^(th) MPM candidate, andcandModeList[5] may denote a 5^(th) MPM candidate. In the MPM listderivation process shown below, IntraLumaRefLineIdx[xCb][yCb] denotesthe reference line index of the block to be predicted, andIntraLumaRefLineIdx[xCb][yCb] can be 0, 1, or 3.

-   -   If candIntraPredModeB is equal to candIntraPredModeA and        candIntraPredModeA is greater than INTRA_DC, candModeList[x]        with x=0.5 is derived as follows:        -   If IntraLumaRefLineIdx[xCb][yCb] is equal to 0, the            following applies:            -   candModeList[0]=candIntraPredModeA            -   candModeList[1]=INTRA_PLANAR            -   candModeList[2]=INTRA_DC            -   candModeList[3]=2+((candIntraPredModeA+61) % 64)            -   candModeList[4]=2+((candIntraPredModeA−1) % 64)            -   candModeList[5]=2+((candIntraPredModeA+60)% 64)        -   Otherwise (IntraLumaRefLineIdx[xCb][yCb] is not equal to 0),            the following applies:            -   candModeList[0]=candIntraPredModeA            -   candModeList[1]=2+((candIntraPredModeA+61) % 64)            -   candModeList[2]=2+((candIntraPredModeA−1) % 64)            -   candModeList[3]=2+((candIntraPredModeA+60)% 64)            -   candModeList[4]=2+(candIntraPredModeA % 64)            -   candModeList[5]=2+((candIntraPredModeA+59) % 64)    -   Otherwise if candIntraPredModeB is not equal to        candIntraPredModeA and candIntraPredModeA or candIntraPredModeB        is greater than INTRA_DC, the following applies:        -   The variables minAB and maxAB are derived as follows:            -   minAB=candModeList[(candModeList[0]>candModeList[1])?                1:0]            -   maxAB=candModeList[(candModeList[0]>candModeList[1])?                0:1]        -   If candIntraPredModeA and candIntraPredModeB are both            greater than INTRA_DC, candModeList[x] with x=0 to 5 is            derived as follows:            -   candModeList[0]=candIntraPredModeA            -   candModeList[1]=candIntraPredModeB        -   If IntraLumaRefLineIdx[xCb][yCb] is equal to 0, the            following applies:            -   candModeList[2]=INTRA_PLANAR            -   candModeList[3]=INTRA_DC            -   If maxAB−minAB is in the range of 2 to 62, inclusive,                the following applies:                -   candModeList[4]=2+((maxAB+61) % 64)                -   candModeList[5]=2+((maxAB−1) % 64)            -   Otherwise, the following applies:                -   candModeList[4]=2+((maxAB+60) % 64)                -   candModeList[5]=2+((maxAB) % 64)        -   Otherwise (IntraLumaRefLineIdx[xCb][yCb] is not equal to 0),            the following applies:            -   If maxAB−minAB is equal to 1, the following applies:                -   candModeList[2]=2+((minAB+61) % 64)                -   candModeList[3]=2+((maxAB−1) % 64)                -   candModeList[4]=2+((minAB+60) % 64)                -   candModeList[5]=2+(maxAB % 64)            -   Otherwise if maxAB−minAB is equal to 2, the following                applies:                -   candModeList[2]=2+((minAB−1) % 64)                -   candModeList[3]=2+((minAB+61) % 64)                -   candModeList[4]=2+((maxAB−1) % 64)                -   candModeList[5]=2+((minAB+60) % 64)            -   Otherwise if maxAB−minAB is greater than 61, the                following applies:                -   candModeList[2]=2+((minAB−1) % 64)                -   candModeList[3]=2+((maxAB+61) % 64)                -   candModeList[4]=2+(minAB % 64)                -   candModeList[5]=2+((maxAB+60) % 64)            -   Otherwise, the following applies:                -   candModeList[2]=2+((minAB+61) % 64)                -   candModeList[3]=2+((minAB−1) % 64)                -   candModeList[4]=2+((maxAB+61) % 64)                -   candModeList[5]=2+((maxAB−1) % 64)    -   Otherwise (candIntraPredModeA or candIntraPredModeB is greater        than INTRA_DC), candModeList[x] with x=0 to 5 is derived as        follows:        -   If IntraLumaRefLineIdx[xCb][yCb] is equal to 0, the            following applies:            -   candModeList[0]=candIntraPredModeA            -   candModeList[1]=candIntraPredModeB            -   candModeList[2]=1−minAB            -   candModeList[3]=2+((maxAB+61) % 64)            -   candModeList[4]=2+((maxAB−1) % 64)            -   candModeList[5]=2+((maxAB+60) % 64)        -   Otherwise (IntraLumaRefLineIdx[xCb][yCb] is not equal to 0),            the following applies:            -   candModeList[0]=maxAB            -   candModeList[1]=2+((maxAB+61) % 64)            -   candModeList[2]=2+((maxAB−1) % 64)            -   candModeList[3]=2+((maxAB+60) % 64)            -   candModeList[4]=2+(maxAB % 64)            -   candModeList[5]=2+((maxAB+59) % 64)    -   Otherwise, the following applies:        -   If IntraLumaRefLineIdx[xCb][yCb] is equal to 0, the            following applies:            -   candModeList[0]=candIntraPredModeA candModeList[1]=            -   (candModeList[0]==INTRA_PLANAR)? INTRA_DC INTRA_PLANAR            -   candModeList[2]=INTRA_ANGULAR50            -   candModeList[3]=INTRA_ANGULAR18            -   candModeList[4]=INTRA_ANGULAR46            -   candModeList[5]=INTRA_ANGULAR54        -   Otherwise (IntraLumaRefLineIdx[xCb][yCb] is not equal to 0),            the following applies:            -   candModeList[0]=INTRA_ANGULAR50            -   candModeList[1]=INTRA_ANGULAR18            -   candModeList[2]=INTRA_ANGULAR2            -   candModeList[3]=INTRA_ANGULAR34            -   candModeList[4]=INTRA_ANGULAR66            -   candModeList[5]=INTRA_ANGULAR26

In VTM4.0, the size of MWM list is extended to 6. Whenintra_luma_mpm_flag is true, it indicates that current mode belongs tothe candidates in WIM list. Consider Table 1 below:

TABLE 1 Descriptor coding_unit( x0, y0, cbWidth, cbHeight, treeType ) { if( tile_group_type != I | | sps_ibc_enabled_flag ) {   if( treeType!=DUAL_TREE_CHROMA )    cu_skip_flag[ x0 ][ y0 ] ae(v)   if(cu_skip_flag[ x0 ][ y0 ] = = 0 && tile_group_type != I )   pred_mode_flag ae(v)   if( ( ( tile_group_type = = I && cu_skip_flag[x0 ][ y0 ] = =0) | |    ( tile_group_type != I && CuPredMode[ x0 ][ y0 ]!= MODE_INTRA ) ) &&    sps_ibc_enabled_flag )    pred_mode_ibc_flagae(v)  }  if( CuPredMode[ x0 ][ y0 ] = = MODE_INTRA ) {   if(sps_pcm_enabled_flag &&    cbWidth >= MinIpcmCbSizeY && cbWidth <=MaxIpcmCbSizeY &&    cbHeight >= MinIpcmCbSizeY && cbHeight <=MaxIpcmCbSizeY )    pcm_flag[ x0 ][ y0 ] ae(v)   if( pcm_flag[ x0][ y0 ]) {    while( !byte_aligned( ) )   pcm_alignment_zero_bit f(1)   pcm_sample( cbWidth, cbHeight, treeType)  } else {    if( treeType == SINGLE_TREE | | treeType = = DUAL_TREE_LUMA ) {     if( ( y0 %CtbSizeY ) > 0)    intra_luma_ref idx[ x0 ][ y0 ] ae(v)     if(intra_luma_ref idx[ x0 ][ y0 ] = = 0 &&      ( cbWidth <= MaxTbSizeY || cbHeight <= MaxTbSizeY ) &&      ( cbWidth * cbHeight > MinTbSizeY *MinTbSizeY ))    intra_subpartitions_mode_flag[ x0 ][ y0 ] ae(v)   if(intra_subpartitions_mode_flag[ x0 ][ y0 ] = = 1 &&    cbWidth <=MaxTbSizeY && cbHeight <= MaxTbSizeY )   intra_subpartitions_split_flag[ x0 ][ y0 ] ae(v)     if(intra_luma_ref idx[ x0 ][ y0 ] = = 0 &&     intra_subpartitions_mode_flag[ x0 ][ y0 ] = = 0 )     intra_luma_mpm_flag[ x0 ][ y0 ] ae(v)     if( intra_luma_mpm_flag[x0 ] [ y0 ])      intra_luma_mpm_idx[ x0 ][ y0 ] ae(v)     else   intra_luma_mpm_remainder[ x0 ][ y0 ] ae(v)    }    if( treeType = =SINGLE_TREE | | treeType = = DUAL_TREE_CHROMA )    intra_chroma_pred_mode[ x0 ][ y0 ] ae(v)   }

The Intra Sub-Partitions (ISP) coding mode divides luma intra-predictedblocks vertically or horizontally into 2 or 4 sub-partitions dependingon the block size dimensions, as shown in Table 2. FIG. 5 and FIG. 6show examples of the two possibilities. All sub-partitions fulfill thecondition of having at least 16 samples.

TABLE 2 Number of sub-partitions depending on the block size Block SizeNumber of Sub-Partitions 4 × 4 Not divided 4 × 8 and 8 × 4 2 All othercases 4

For each of these sub-partitions, a residual signal may be generated byentropy decoding the coefficients sent by the encoder and then inversequantizing and inverse transforming them. Then, the sub-partition may beintra predicted and finally the corresponding reconstructed samples areobtained by adding the residual signal to the prediction signal.Therefore, the reconstructed values of each sub-partition will beavailable to generate the prediction of the next one, which will repeatthe process and so on. All sub-partitions may share the same intra mode.

Based on the intra mode and the split utilized, two different classes ofprocessing orders may be used, which are referred to as normal andreversed order. In the normal order, the first sub-partition to beprocessed is the one containing the top-left sample of the CU and thencontinuing downwards in a horizontal split, or rightwards in a verticalsplit. As a result, reference samples used to generate thesub-partitions prediction signals are only located at the left and abovesides of the lines. On the other hand, the reverse processing ordereither starts with the sub-partition containing the bottom-left sampleof the CU and continues upwards or starts with sub-partition containingthe top-right sample of the CU and continues leftwards.

The ISP algorithm may be tested with intra modes that are part of theMPM list. For this reason, if a block uses ISP, then the MPM flag may beinferred to be one. Besides, if ISP is used for a certain block, thenthe MPM list may be modified to exclude the DC mode and to prioritizehorizontal intra modes for the ISP horizontal split and vertical intramodes for the vertical one.

FIG. 7 illustrates a simplified block diagram of a communication system(300) according to an embodiment of the present disclosure. Thecommunication system (300) may include at least two terminals (710-720)interconnected via a network (750). For unidirectional transmission ofdata, a first terminal (710) may code video data at a local location fortransmission to the other terminal (720) via the network (750). Thesecond terminal (720) may receive the coded video data of the otherterminal from the network (750), decode the coded data and display therecovered video data. Unidirectional data transmission may be common inmedia serving applications and the like.

FIG. 7 illustrates a second pair of terminals (730, 740) provided tosupport bidirectional transmission of coded video that may occur, forexample, during videoconferencing. For bidirectional transmission ofdata, each terminal (730, 740) may code video data captured at a locallocation for transmission to the other terminal via the network (750).Each terminal (730, 740) also may receive the coded video datatransmitted by the other terminal, may decode the coded data and maydisplay the recovered video data at a local display device.

In FIG. 7, the terminals (710-740) may be illustrated as servers,personal computers and smart phones but the principles of the presentdisclosure are not so limited. Embodiments of the present disclosurefind application with laptop computers, tablet computers, media playersand/or dedicated video conferencing equipment. The network (750)represents any number of networks that convey coded video data among theterminals (710-740), including for example wireline and/or wirelesscommunication networks. The communication network (750) may exchangedata in circuit-switched and/or packet-switched channels. Representativenetworks include telecommunications networks, local area networks, widearea networks and/or the Internet. For the purposes of the presentdiscussion, the architecture and topology of the network (750) may beimmaterial to the operation of the present disclosure unless explainedherein below.

FIG. 8 illustrates, as an example for an application for the disclosedsubject matter, the placement of a video encoder and decoder in astreaming environment. The disclosed subject matter can be equallyapplicable to other video enabled applications, including, for example,video conferencing, digital TV, storing of compressed video on digitalmedia including CD, DVD, memory stick and the like, and so on.

A streaming system may include a capture subsystem (813), that caninclude a video source (801), for example a digital camera, creating,for example, an uncompressed video sample stream (802). That samplestream (802), depicted as a bold line to emphasize a high data volumewhen compared to encoded video bitstreams, can be processed by anencoder (803) coupled to the camera 801). The encoder (803) can includehardware, software, or a combination thereof to enable or implementaspects of the disclosed subject matter as described in more detailbelow. The encoded video bitstream (804), depicted as a thin line toemphasize the lower data volume when compared to the sample stream, canbe stored on a streaming server (805) for future use. One or morestreaming clients (806, 808) can access the streaming server (805) toretrieve copies (807, 809) of the encoded video bitstream (804). Aclient (806) can include a video decoder (810) which decodes theincoming copy of the encoded video bitstream (807) and creates anoutgoing video sample stream (811) that can be rendered on a display(812) or other rendering device (not depicted). In some streamingsystems, the video bitstreams (804, 807, 809) can be encoded accordingto certain video coding/compression standards. Examples of thosestandards include ITU-T Recommendation H.265. Under development is avideo coding standard informally known as Versatile Video Coding (VVC).The disclosed subject matter may be used in the context of VVC.

FIG. 9 may be a functional block diagram of a video decoder (810)according to an embodiment of the present invention.

A receiver (910) may receive one or more codec video sequences to bedecoded by the decoder (810); in the same or another embodiment, onecoded video sequence at a time, where the decoding of each coded videosequence is independent from other coded video sequences. The codedvideo sequence may be received from a channel (912), which may be ahardware/software link to a storage device which stores the encodedvideo data. The receiver (910) may receive the encoded video data withother data, for example, coded audio data and/or ancillary data streams,that may be forwarded to their respective using entities (not depicted).The receiver (910) may separate the coded video sequence from the otherdata. To combat network jitter, a buffer memory (915) may be coupled inbetween receiver (910) and entropy decoder/parser (920) (“parser”henceforth). When receiver (910) is receiving data from a store/forwarddevice of sufficient bandwidth and controllability, or from anisosychronous network, the buffer (915) may not be needed, or can besmall. For use on best effort packet networks such as the Internet, thebuffer (915) may be required, can be comparatively large and canadvantageously of adaptive size.

The video decoder (810) may include a parser (920) to reconstructsymbols (921) from the entropy coded video sequence. Categories of thosesymbols include information used to manage operation of the decoder(810), and potentially information to control a rendering device such asa display (812) that is not an integral part of the decoder but can becoupled to it, as was shown in FIG. 9. The control information for therendering device(s) may be in the form of Supplementary EnhancementInformation (SEI messages) or Video Usability Information (VUI)parameter set fragments (not depicted). The parser (920) mayparse/entropy-decode the coded video sequence received. The coding ofthe coded video sequence can be in accordance with a video codingtechnology or standard, and can follow principles well known to a personskilled in the art, including variable length coding, Huffman coding,arithmetic coding with or without context sensitivity, and so forth. Theparser (920) may extract from the coded video sequence, a set ofsubgroup parameters for at least one of the subgroups of pixels in thevideo decoder, based upon at least one parameters corresponding to thegroup. Subgroups can include Groups of Pictures (GOPs), pictures, tiles,slices, macroblocks, Coding Units (CUs), blocks, Transform Units (TUs),Prediction Units (PUs) and so forth. The entropy decoder/parser may alsoextract from the coded video sequence information such as transformcoefficients, quantizer parameter (QP) values, motion vectors, and soforth.

The parser (920) may perform entropy decoding/parsing operation on thevideo sequence received from the buffer (915), so to create symbols(921). The parser (920) may receive encoded data, and selectively decodeparticular symbols (921). Further, the parser (920) may determinewhether the particular symbols (921) are to be provided to a MotionCompensation Prediction unit (953), a scaler/inverse transform unit(951), an Intra Prediction Unit (952), or a loop filter (956).

Reconstruction of the symbols (921) can involve multiple different unitsdepending on the type of the coded video picture or parts thereof (suchas: inter and intra picture, inter and intra block), and other factors.Which units are involved, and how, can be controlled by the subgroupcontrol information that was parsed from the coded video sequence by theparser (920). The flow of such subgroup control information between theparser (920) and the multiple units below is not depicted for clarity.

Beyond the functional blocks already mentioned, decoder (810) can beconceptually subdivided into a number of functional units as describedbelow. In a practical implementation operating under commercialconstraints, many of these units interact closely with each other andcan, at least partly, be integrated into each other. However, for thepurpose of describing the disclosed subject matter, the conceptualsubdivision into the functional units below is appropriate.

A first unit is the scaler/inverse transform unit (951). Thescaler/inverse transform unit (951) receives quantized transformcoefficient as well as control information, including which transform touse, block size, quantization factor, quantization scaling matrices,etc. as symbol(s) (621) from the parser (920). It can output blockscomprising sample values, that can be input into aggregator (955).

In some cases, the output samples of the scaler/inverse transform (951)can pertain to an intra coded block; that is: a block that is not usingpredictive information from previously reconstructed pictures, but canuse predictive information from previously reconstructed parts of thecurrent picture. Such predictive information can be provided by an intrapicture prediction unit (952). In some cases, the intra pictureprediction unit (952) generates a block of the same size and shape ofthe block under reconstruction, using surrounding already reconstructedinformation fetched from the current (partly reconstructed) picture(956). The aggregator (955), in some cases, adds, on a per sample basis,the prediction information the intra prediction unit (952) has generatedto the output sample information as provided by the scaler/inversetransform unit (951).

In other cases, the output samples of the scaler/inverse transform unit(951) can pertain to an inter coded, and potentially motion compensatedblock. In such a case, a Motion Compensation Prediction unit (953) canaccess reference picture memory (957) to fetch samples used forprediction. After motion compensating the fetched samples in accordancewith the symbols (921) pertaining to the block, these samples can beadded by the aggregator (955) to the output of the scaler/inversetransform unit (in this case called the residual samples or residualsignal) so to generate output sample information. The addresses withinthe reference picture memory form where the motion compensation unitfetches prediction samples can be controlled by motion vectors,available to the motion compensation unit in the form of symbols (921)that can have, for example X, Y, and reference picture components.Motion compensation also can include interpolation of sample values asfetched from the reference picture memory when sub-sample exact motionvectors are in use, motion vector prediction mechanisms, and so forth.

The output samples of the aggregator (955) can be subject to variousloop filtering techniques in the loop filter unit (956). Videocompression technologies can include in-loop filter technologies thatare controlled by parameters included in the coded video bitstream andmade available to the loop filter unit (956) as symbols (921) from theparser (920), but can also be responsive to meta-information obtainedduring the decoding of previous (in decoding order) parts of the codedpicture or coded video sequence, as well as responsive to previouslyreconstructed and loop-filtered sample values.

The output of the loop filter unit (956) can be a sample stream that canbe output to the render device (812) as well as stored in the referencepicture memory (956) for use in future inter-picture prediction.

Certain coded pictures, once fully reconstructed, can be used asreference pictures for future prediction. Once a coded picture is fullyreconstructed and the coded picture has been identified as a referencepicture (by, for example, parser (920)), the current reference picture(656) can become part of the reference picture buffer (957), and a freshcurrent picture memory can be reallocated before commencing thereconstruction of the following coded picture.

The video decoder (810) may perform decoding operations according to apredetermined video compression technology that may be documented in astandard, such as ITU-T Rec. H.265. The coded video sequence may conformto a syntax specified by the video compression technology or standardbeing used, in the sense that it adheres to the syntax of the videocompression technology or standard, as specified in the videocompression technology document or standard and specifically in theprofiles document therein. Also necessary for compliance can be that thecomplexity of the coded video sequence is within bounds as defined bythe level of the video compression technology or standard. In somecases, levels restrict the maximum picture size, maximum frame rate,maximum reconstruction sample rate (measured in, for example megasamplesper second), maximum reference picture size, and so on. Limits set bylevels can, in some cases, be further restricted through HypotheticalReference Decoder (HRD) specifications and metadata for HRD buffermanagement signaled in the coded video sequence.

In an embodiment, the receiver (910) may receive additional (redundant)data with the encoded video. The additional data may be included as partof the coded video sequence(s). The additional data may be used by thevideo decoder (810) to properly decode the data and/or to moreaccurately reconstruct the original video data. Additional data can bein the form of, for example, temporal, spatial, or signal-to-noise ratio(SNR) enhancement layers, redundant slices, redundant pictures, forwarderror correction codes, and so on.

FIG. 10 may be a functional block diagram of a video encoder (803)according to an embodiment of the present disclosure.

The encoder (803) may receive video samples from a video source (801)(that is not part of the encoder) that may capture video image(s) to becoded by the encoder (803).

The video source (801) may provide the source video sequence to be codedby the encoder (803) in the form of a digital video sample stream thatcan be of any suitable bit depth (for example: 8 bit, 10 bit, 12 bit, .. . ), any colorspace (for example, BT.601 Y CrCB, RGB, . . . ) and anysuitable sampling structure (for example Y CrCb 4:2:0, Y CrCb 4:4:4). Ina media serving system, the video source (801) may be a storage devicestoring previously prepared video. In a videoconferencing system, thevideo source (803) may be a camera that captures local image informationas a video sequence. Video data may be provided as a plurality ofindividual pictures that impart motion when viewed in sequence. Thepictures themselves may be organized as a spatial array of pixels,wherein each pixel can comprise one or more samples depending on thesampling structure, color space, etc. in use. A person skilled in theart can readily understand the relationship between pixels and samples.The description below focuses on samples.

According to an embodiment, the encoder (803) may code and compress thepictures of the source video sequence into a coded video sequence (1043)in real time or under any other time constraints as required by theapplication. Enforcing appropriate coding speed is one function ofController (1050). Controller controls other functional units asdescribed below and is functionally coupled to these units. The couplingis not depicted for clarity. Parameters set by controller can includerate control related parameters (picture skip, quantizer, lambda valueof rate-distortion optimization techniques, . . . ), picture size, groupof pictures (GOP) layout, maximum motion vector search range, and soforth. A person skilled in the art can readily identify other functionsof controller (1050) as they may pertain to video encoder (803)optimized for a certain system design.

Some video encoders operate in what a person skilled in the art readilyrecognizes as a “coding loop.” As an oversimplified description, acoding loop can consist of the encoding part of an encoder (1030)(“source coder” henceforth) (responsible for creating symbols based onan input picture to be coded, and a reference picture(s)), and a (local)decoder (1033) embedded in the encoder (803) that reconstructs thesymbols to create the sample data that a (remote) decoder also wouldcreate (as any compression between symbols and coded video bitstream islossless in the video compression technologies considered in thedisclosed subject matter). That reconstructed sample stream is input tothe reference picture memory (1034). As the decoding of a symbol streamleads to bit-exact results independent of decoder location (local orremote), the reference picture buffer content is also bit exact betweenlocal encoder and remote encoder. In other words, the prediction part ofan encoder “sees” as reference picture samples exactly the same samplevalues as a decoder would “see” when using prediction during decoding.This fundamental principle of reference picture synchronicity (andresulting drift, if synchronicity cannot be maintained, for examplebecause of channel errors) is well known to a person skilled in the art.

The operation of the “local” decoder (1033) can be the same as of a“remote” decoder (810), which has already been described in detail abovein conjunction with FIG. 9. Briefly referring also to FIG. 6, however,as symbols are available and en/decoding of symbols to a coded videosequence by entropy coder (1045) and parser (920) can be lossless, theentropy decoding parts of decoder (810), including channel (912),receiver (910), buffer (915), and parser (920) may not be fullyimplemented in local decoder (1033).

An observation that can be made at this point is that any decodertechnology except the parsing/entropy decoding that is present in adecoder also necessarily needs to be present, in substantially identicalfunctional form, in a corresponding encoder. The description of encodertechnologies can be abbreviated as they are the inverse of thecomprehensively described decoder technologies. Only in certain areas amore detail description is required and provided below.

As part of its operation, the source coder (1030) may perform motioncompensated predictive coding, which codes an input frame predictivelywith reference to one or more previously-coded frames from the videosequence that were designated as “reference frames.” In this manner, thecoding engine (1032) codes differences between pixel blocks of an inputframe and pixel blocks of reference frame(s) that may be selected asprediction reference(s) to the input frame.

The local video decoder (1033) may decode coded video data of framesthat may be designated as reference frames, based on symbols created bythe source coder (1030). Operations of the coding engine (1032) mayadvantageously be lossy processes. When the coded video data may bedecoded at a video decoder (not shown in FIG. 6), the reconstructedvideo sequence typically may be a replica of the source video sequencewith some errors. The local video decoder (1033) replicates decodingprocesses that may be performed by the video decoder on reference framesand may cause reconstructed reference frames to be stored in thereference picture cache (1034). In this manner, the encoder (803) maystore copies of reconstructed reference frames locally that have commoncontent as the reconstructed reference frames that will be obtained by afar-end video decoder (absent transmission errors).

The predictor (1035) may perform prediction searches for the codingengine (1032). That is, for a new frame to be coded, the predictor(1035) may search the reference picture memory (1034) for sample data(as candidate reference pixel blocks) or certain metadata such asreference picture motion vectors, block shapes, and so on, that mayserve as an appropriate prediction reference for the new pictures. Thepredictor (1035) may operate on a sample block-by-pixel block basis tofind appropriate prediction references. In some cases, as determined bysearch results obtained by the predictor (1035), an input picture mayhave prediction references drawn from multiple reference pictures storedin the reference picture memory (1034).

The controller (1050) may manage coding operations of the video coder(1030), including, for example, setting of parameters and subgroupparameters used for encoding the video data.

Output of all aforementioned functional units may be subjected toentropy coding in the entropy coder (1045). The entropy coder translatesthe symbols as generated by the various functional units into a codedvideo sequence, by loss-less compressing the symbols according totechnologies known to a person skilled in the art as, for exampleHuffman coding, variable length coding, arithmetic coding, and so forth.

The transmitter (1040) may buffer the coded video sequence(s) as createdby the entropy coder (1045) to prepare it for transmission via acommunication channel (1060), which may be a hardware/software link to astorage device which would store the encoded video data. The transmitter(1040) may merge coded video data from the video coder (1030) with otherdata to be transmitted, for example, coded audio data and/or ancillarydata streams (sources not shown).

The controller (1050) may manage operation of the encoder (803). Duringcoding, the controller (1050) may assign to each coded picture a certaincoded picture type, which may affect the coding techniques that may beapplied to the respective picture. For example, pictures often may beassigned as one of the following frame types:

An Intra Picture (I picture) may be one that may be coded and decodedwithout using any other frame in the sequence as a source of prediction.Some video codecs allow for different types of Intra pictures,including, for example Independent Decoder Refresh Pictures. A personskilled in the art is aware of those variants of I pictures and theirrespective applications and features.

A Predictive picture (P picture) may be one that may be coded anddecoded using intra prediction or inter prediction using at most onemotion vector and reference index to predict the sample values of eachblock.

A Bi-directionally Predictive Picture (B Picture) may be one that may becoded and decoded using intra prediction or inter prediction using atmost two motion vectors and reference indices to predict the samplevalues of each block. Similarly, multiple-predictive pictures can usemore than two reference pictures and associated metadata for thereconstruction of a single block.

Source pictures commonly may be subdivided spatially into a plurality ofsample blocks (for example, blocks of 4×4, 8×8, 4×8, or 16×16 sampleseach) and coded on a block-by-block basis. Blocks may be codedpredictively with reference to other (already coded) blocks asdetermined by the coding assignment applied to the blocks' respectivepictures. For example, blocks of I pictures may be codednon-predictively or they may be coded predictively with reference toalready coded blocks of the same picture (spatial prediction or intraprediction). Pixel blocks of P pictures may be coded non-predictively,via spatial prediction or via temporal prediction with reference to onepreviously coded reference pictures. Blocks of B pictures may be codednon-predictively, via spatial prediction or via temporal prediction withreference to one or two previously coded reference pictures.

The video coder (803) may perform coding operations according to apredetermined video coding technology or standard, such as ITU-T Rec.H.265. In its operation, the video coder (803) may perform variouscompression operations, including predictive coding operations thatexploit temporal and spatial redundancies in the input video sequence.The coded video data, therefore, may conform to a syntax specified bythe video coding technology or standard being used.

In an embodiment, the transmitter (1040) may transmit additional datawith the encoded video. The video coder (1030) may include such data aspart of the coded video sequence. Additional data may comprisetemporal/spatial/SNR enhancement layers, other forms of redundant datasuch as redundant pictures and slices, Supplementary EnhancementInformation (SEI) messages, Visual Usability Information (VUI) parameterset fragments, and so on.

As discussed above, in VTM3.0, MPM list candidate derivation process maybe different for adjacent reference line with ISP mode disabled,adjacent reference lines with ISP mode enabled, and non-adjacentreference lines. As a result, MPM list candidate derivation process maybe complicated in each case without clear benefit in coding efficiency.

In embodiments, the line index of the nearest reference line may be 0,and the nearest reference line may be referred to as the zero referenceline, or the adjacent reference line. Other lines may be referred to asnon-zero reference lines, or non-adjacent reference lines. In thedescription below, candModeList may denote the MPM list, RefLineIdx maydenote the reference line index of current block, candIntraPredModeA andcandIntraPredModeB may denote the left and above neighboring modes. Ifone neighboring mode is not Planar or DC mode, or one neighboring modeis generating prediction samples according a given prediction direction,such as intra prediction modes 2 through 66 as defined in VVC draft 2,this mode may be referred to as an angular mode. If one mode is notindicating an directional intra prediction, such as in Planar or DCmode, this mode may be referred to as a non-angular mode. Each intraprediction mode may be associated with a mode number, which may bereferred to as an intra prediction mode index. For example, Planar, DC,horizontal and vertical intra prediction modes may be associated withmode number 0, 1, 18 and 50, respectively.

In an embodiment, the MPM index of the first candidate in the MPM listmay be denoted as 0, and the MPM index of second candidate may bedenoted as 1, and so on.

In an embodiment, the variables minAB and maxAB may be derived asfollows:

-   -   candModeList[0]=candIntraPredModeA    -   candModeList[1]=candIntraPredModeB    -   minAB=candModeList[(candModeList[0]>candModeList[1])? 1:0]    -   maxAB=candModeList[(candModeList[0]>candModeList[1])? 0:1]

In an embodiment, the variables offset and mod may be set according toeither one of the following two scenarios: offset=61, mod=64; offset=62,mod=65.

In an embodiment, for an adjacent reference line with ISP mode disabled,an adjacent reference line with ISP mode enabled, and non-adjacentreference lines, the same MPM list construction process may be sharedand the order of candidates may be the same.

In an embodiment, Planar and DC modes may be always included into theMPM list, and the number of derived angular intra prediction modes maybe set equal to N. N may be a positive integer, such as 1, 2, 3, 4, 5,or 6.

In an embodiment, the ISP related syntax elements may be signaled afterreference line index, and if reference line index is a default valuewhich indicates the adjacent reference line is used.

In one embodiment, the reference line index related syntax elements maybe signaled after the ISP related syntax elements and if ISP relatedsyntax elements are signaled with a value which indicates ISP mode isnot used.

In another embodiment, all the candidates in the MPM list can be usedfor zero reference line with ISP mode disabled.

In another embodiment, all the candidates except DC mode in the MPM listcan be used for adjacent reference line with ISP mode enabled.

In another embodiment, all the candidates except Planar and DC modes inthe MPM list can be used for non-adjacent reference lines.

In another embodiment, Planar mode may be always firstly inserted intothe MPM list with index 0.

In an embodiment, Planar and DC modes may be always firstly insertedinto the MPM list with index 0 and 1.

In another embodiment, the signaling of MPM index may be context coded,and the context depends on whether the neighboring blocks may be codedby angular prediction mode.

In another embodiment, the signaling of MPM index may be context coded,and the context depends on MPM index (and/or MPM flag) of theneighboring blocks.

In an embodiment, the signaling of first K bins of MPM index may becontext coded, and the context depends on MPM index and reference lineindex (and/or MPM flag) of the neighboring blocks. K may be a positiveinteger, such as 1 or 2.

In an embodiment, the first K bins of MPM index is context coded, andthe context depends on MPM index, ISP flag, and reference line index(and/or MPM flag) of the neighboring blocks.

In another embodiment, the first K bins of MPM index may be contextcoded, and other bins of MPM indices are bypass coded.

In another embodiment, the neighboring blocks used here may be the sameas the neighboring blocks used for MPM list generation.

In one embodiment, when the reference line index is signaled as zero,the first K bins, for example the first two bins, of MPM index may becontext coded, and the context may depend on whether ISP mode is enabledand/or the reference line index value of current block.

In one embodiment, when the reference line index is signaled as zero,the first K bins, for example the first two bins, of MPM index may becontext coded, and the context may depend on MPM index and referenceline index (and/or MPM flag) of the neighboring blocks.

In another embodiment, for the first K bins of MPM index, 3 contexts maybe used. If both MPM flags of the neighboring blocks are true, referenceline index is 0, and MPM indices are equal to or smaller than Th, onecontext is used; Otherwise, if only one of the MPM flag of theneighboring blocks is true, reference line index is 0, and MPM index isequal to or smaller than Th, a second context may be used. Otherwise,the third context may be used. Th may be a positive integer, such as 1,2 or 3.

In another embodiment, when the reference line index is signaled as zeroand ISP is set equal to false for current block, for the second bin ofMPM index, the second bin of MPM index may be context coded. If both MPMflags of the neighboring blocks are true, reference line index is equalto 0, and MPM indices are equal to 1 (or 0), one context may be used;Otherwise, if only one of the MPM flag of the neighboring blocks istrue, reference line index is equal to 0, and MPM index is equal to 1(or 0), a second context may be used. Otherwise, the third context maybe used.

In an embodiment, for adjacent reference lines with ISP flag equal totrue and non-adjacent reference lines, MPM list candidates may bederived by using the same rule if the absolute mode number differencebetween left and above neighboring modes is larger than or equal to agiven threshold value.

In an embodiment, the given threshold value is 0, which means, MPM listcandidates are derived by using the same rule regardless of the modenumber difference between left and above neighboring modes.

In another embodiment, if left and above neighboring modes are notequal, MPM list candidates may be derived by using the same ruleregardless of the mode number difference between left and aboveneighboring modes.

In an embodiment, if the left and above neighboring modes are bothangular modes but they are not equal, MPM list candidates are derived byusing the same rule regardless of the mode number difference betweenleft and above neighboring modes.

In one example, 6 MPM candidates are derived as follows:

-   -   candModeList[0]=candIntraPredModeA    -   candModeList[1]=candIntraPredModeB    -   candModeList[2]=2+((minAB+offset) % mod)    -   candModeList[3]=2+((minAB−1) % mod)    -   candModeList[4]=2+((maxAB+offset) % mod)    -   candModeList[5]=2+((maxAB−1) % mod)

In another example, 6 MPM candidates are derived as follows:

-   -   candModeList[0]=candIntraPredModeA    -   candModeList[1]=candIntraPredModeB    -   candModeList[2]=2+((minAB+offset) % mod)    -   candModeList[3]=2+((maxAB−1) % mod)    -   candModeList[4]=2+((minAB−1) % mod)    -   candModeList[5]=2+((maxAB+offset) % mod)

In another example, 6 MPM candidates are derived as follows:

-   -   candModeList[0]=candIntraPredModeA    -   candModeList[1]=candIntraPredModeB    -   candModeList[2]=2+((maxAB+offset) % mod)    -   candModeList[3]=2+((maxAB−1) % mod)    -   candModeList[4]=2+((minAB+offset) % mod)    -   candModeList[5]=2+((minAB−1) % mod)

In another example, 6 MPM candidates are derived as follows:

-   -   candModeList[0]=candIntraPredModeA    -   candModeList[1]=candIntraPredModeB    -   candModeList[2]=2+((candIntraPredModeA+offset) % mod)    -   candModeList[3]=2+((candIntraPredModeA−1) % mod)    -   candModeList[4]=2+((candIntraPredModeB+offset) % mod)    -   candModeList[5]=2+((candIntraPredModeB−1) % mod)

In another embodiment, if at least one of the left and above is angularmode, MPM list candidates may be derived by using the same ruleregardless of the mode number difference between left and aboveneighboring modes.

In an embodiment, when both the left and above neighboring modes arenon-angular modes, default modes are used to fill the MPM candidatelist, the angular default modes are the same for adjacent reference linewith ISP flag equal to false, adjacent reference line with ISP flagequal to true, and non-adjacent reference line.

In an embodiment, the default angular modes may be {50, 18, 2, 34}.

In another embodiment, the default angular modes may be {50, 18, 34,66}.

FIG. 11 is a flowchart of an example process 1100 for signaling an intraprediction mode used to encode a current block in an encoded videobitstream. In some implementations, one or more process blocks of FIG.11 may be performed by decoder 810. In some implementations, one or moreprocess blocks of FIG. 11 may be performed by another device or a groupof devices separate from or including decoder 810, such as encoder 803.

As shown in FIG. 11, process 1100 may include determining a plurality ofcandidate intra prediction modes (block 1110).

As further shown in FIG. 11, process 1100 may include generating a mostprobable mode (MPM) list using the plurality of candidate intraprediction modes (block 1120).

As further shown in FIG. 11, process 1100 may include signaling areference line index indicating a reference line used to encode thecurrent block from among a plurality of reference lines including anadjacent reference line and a plurality of non-adjacent reference lines(block 1130).

As further shown in FIG. 11, process 1100 may include signaling an intramode index indicating the intra prediction mode (block 1140).

In an embodiment, the MPM list may be generated based on the referenceline used to encode the current block and whether an intra sub-partition(ISP) mode is enabled.

In an embodiment, based on the reference line being the adjacentreference line and the ISP mode being disabled, the MPM list may includeall of the candidate intra prediction modes.

In an embodiment, based on the reference line being the adjacentreference line and the ISP mode being enabled, the MPM list may includeall of the candidate intra prediction modes except for a DC mode.

In an embodiment, based on the reference line being the one from amongthe plurality of non-adjacent reference lines, the MPM list may includeall of the candidate intra prediction modes except for a DC mode and aplanar mode.

In an embodiment, a first intra prediction mode of the MPM list may be aplanar mode.

In an embodiment, a second intra prediction mode of the MPM list may bea DC mode.

In an embodiment, based on the reference line index indicating that thereference line is the adjacent reference line, a first two bins of theintra mode index are context coded, wherein a context may be determinedbased on whether the ISP mode is enabled.

In an embodiment, based on the reference line index indicating that thereference line is the adjacent reference line, a first two bins of theintra mode index are context coded, wherein a context may be determinedbased on a value of the reference line index.

In an embodiment, based on the reference line index indicating that thereference line is the adjacent reference line, a first two bins of theintra mode index are context coded, wherein a context may be determinedbased on whether the ISP mode is enabled and the reference line index.

In an embodiment, based on the reference line index indicating that thereference line is the adjacent reference line, a first two bins of theintra mode index are context coded, wherein a context may be determinedbased on the intra mode index and a reference line index indicating areference line used to encode a neighboring block.

Although FIG. 11 shows example blocks of process 1100, in someimplementations, process 1100 may include additional blocks, fewerblocks, different blocks, or differently arranged blocks than thosedepicted in FIG. 11. Additionally, or alternatively, two or more of theblocks of process 1100 may be performed in parallel.

Further, the proposed methods may be implemented by processing circuitry(e.g., one or more processors or one or more integrated circuits). Inone example, the one or more processors execute a program that is storedin a non-transitory computer-readable medium to perform one or more ofthe proposed methods.

The techniques described above, can be implemented as computer softwareusing computer-readable instructions and physically stored in one ormore computer-readable media. For example, FIG. 12 shows a computersystem 1200 suitable for implementing certain embodiments of thedisclosed subject matter.

The computer software can be coded using any suitable machine code orcomputer language, that may be subject to assembly, compilation,linking, or like mechanisms to create code comprising instructions thatcan be executed directly, or through interpretation, micro-codeexecution, and the like, by computer central processing units (CPUs),Graphics Processing Units (GPUs), and the like.

The instructions can be executed on various types of computers orcomponents thereof, including, for example, personal computers, tabletcomputers, servers, smartphones, gaming devices, internet of thingsdevices, and the like.

The components shown in FIG. 12 for computer system 1200 are exemplaryin nature and are not intended to suggest any limitation as to the scopeof use or functionality of the computer software implementingembodiments of the present disclosure. Neither should the configurationof components be interpreted as having any dependency or requirementrelating to any one or combination of components illustrated in theexemplary embodiment of a computer system 1200.

Computer system 1200 may include certain human interface input devices.Such a human interface input device may be responsive to input by one ormore human users through, for example, tactile input (such as:keystrokes, swipes, data glove movements), audio input (such as: voice,clapping), visual input (such as: gestures), olfactory input (notdepicted). The human interface devices can also be used to capturecertain media not necessarily directly related to conscious input by ahuman, such as audio (such as: speech, music, ambient sound), images(such as: scanned images, photographic images obtain from a still imagecamera), video (such as two-dimensional video, three-dimensional videoincluding stereoscopic video).

Input human interface devices may include one or more of (only one ofeach depicted): keyboard 1201, mouse 1202, trackpad 1203, touch screen1210, data-glove 1204, joystick 1205, microphone 1206, scanner 1207,camera 1208.

Computer system 1200 may also include certain human interface outputdevices. Such human interface output devices may be stimulating thesenses of one or more human users through, for example, tactile output,sound, light, and smell/taste. Such human interface output devices mayinclude tactile output devices (for example tactile feedback by thetouch-screen 1210, data-glove 1204, or joystick 1205, but there can alsobe tactile feedback devices that do not serve as input devices), audiooutput devices (such as: speakers 1209, headphones (not depicted)),visual output devices (such as screens 1210 to include cathode ray tube(CRT) screens, liquid-crystal display (LCD) screens, plasma screens,organic light-emitting diode (OLED) screens, each with or withouttouch-screen input capability, each with or without tactile feedbackcapability—some of which may be capable to output two dimensional visualoutput or more than three dimensional output through means such asstereographic output; virtual-reality glasses (not depicted),holographic displays and smoke tanks (not depicted)), and printers (notdepicted).

Computer system 1200 can also include human accessible storage devicesand their associated media such as optical media including CD/DVD ROM/RW1220 with CD/DVD or the like media 1221, thumb-drive 1222, removablehard drive or solid state drive 1223, legacy magnetic media such as tapeand floppy disc (not depicted), specialized ROM/ASIC/PLD based devicessuch as security dongles (not depicted), and the like.

Those skilled in the art should also understand that term “computerreadable media” as used in connection with the presently disclosedsubject matter does not encompass transmission media, carrier waves, orother transitory signals.

Computer system 1200 can also include interface(s) to one or morecommunication networks. Networks can for example be wireless, wireline,optical. Networks can further be local, wide-area, metropolitan,vehicular and industrial, real-time, delay-tolerant, and so on. Examplesof networks include local area networks such as Ethernet, wireless LANs,cellular networks to include global systems for mobile communications(GSM), third generation (3G), fourth generation (4G), fifth generation(5G), Long-Term Evolution (LTE), and the like, TV wireline or wirelesswide area digital networks to include cable TV, satellite TV, andterrestrial broadcast TV, vehicular and industrial to include CANBus,and so forth. Certain networks commonly require external networkinterface adapters that attached to certain general purpose data portsor peripheral buses (1249) (such as, for example universal serial bus(USB) ports of the computer system 1200; others are commonly integratedinto the core of the computer system 1200 by attachment to a system busas described below (for example Ethernet interface into a PC computersystem or cellular network interface into a smartphone computer system).Using any of these networks, computer system 1200 can communicate withother entities. Such communication can be uni-directional, receive only(for example, broadcast TV), uni-directional send-only (for exampleCANbus to certain CANbus devices), or bi-directional, for example toother computer systems using local or wide area digital networks.Certain protocols and protocol stacks can be used on each of thosenetworks and network interfaces as described above.

Aforementioned human interface devices, human-accessible storagedevices, and network interfaces can be attached to a core 1240 of thecomputer system 1200.

The core 1240 can include one or more Central Processing Units (CPU)1241, Graphics Processing Units (GPU) 1242, specialized programmableprocessing units in the form of Field Programmable Gate Areas (FPGA)1243, hardware accelerators for certain tasks 1244, and so forth. Thesedevices, along with Read-only memory (ROM) 1245, Random-access memory(RAM) 1246, internal mass storage such as internal non-user accessiblehard drives, solid-state drives (SSDs), and the like 1247, may beconnected through a system bus 1248. In some computer systems, thesystem bus 1248 can be accessible in the form of one or more physicalplugs to enable extensions by additional CPUs, GPU, and the like. Theperipheral devices can be attached either directly to the core's systembus 1248, or through a peripheral bus 1249. Architectures for aperipheral bus include peripheral component interconnect (PCI), USB, andthe like.

CPUs 1241, GPUs 1242, FPGAs 1243, and accelerators 1244 can executecertain instructions that, in combination, can make up theaforementioned computer code. That computer code can be stored in ROM1245 or RAM 1246. Transitional data can be also be stored in RAM 1246,whereas permanent data can be stored for example, in the internal massstorage 1247. Fast storage and retrieve to any of the memory devices canbe enabled through the use of cache memory, that can be closelyassociated with one or more CPU 1241, GPU 1242, mass storage 1247, ROM1245, RAM 1246, and the like.

The computer readable media can have computer code thereon forperforming various computer-implemented operations. The media andcomputer code can be those specially designed and constructed for thepurposes of the present disclosure, or they can be of the kind wellknown and available to those having skill in the computer software arts.

As an example and not by way of limitation, the computer system havingarchitecture 1200, and specifically the core 1240 can providefunctionality as a result of processor(s) (including CPUs, GPUs, FPGA,accelerators, and the like) executing software embodied in one or moretangible, computer-readable media. Such computer-readable media can bemedia associated with user-accessible mass storage as introduced above,as well as certain storage of the core 1240 that are of non-transitorynature, such as core-internal mass storage 1247 or ROM 1245. Thesoftware implementing various embodiments of the present disclosure canbe stored in such devices and executed by core 1240. A computer-readablemedium can include one or more memory devices or chips, according toparticular needs. The software can cause the core 1240 and specificallythe processors therein (including CPU, GPU, FPGA, and the like) toexecute particular processes or particular parts of particular processesdescribed herein, including defining data structures stored in RAM 1246and modifying such data structures according to the processes defined bythe software. In addition or as an alternative, the computer system canprovide functionality as a result of logic hardwired or otherwiseembodied in a circuit (for example: accelerator 1244), which can operatein place of or together with software to execute particular processes orparticular parts of particular processes described herein. Reference tosoftware can encompass logic, and vice versa, where appropriate.Reference to a computer-readable media can encompass a circuit (such asan integrated circuit (IC)) storing software for execution, a circuitembodying logic for execution, or both, where appropriate. The presentdisclosure encompasses any suitable combination of hardware andsoftware.

While this disclosure has described several exemplary embodiments, thereare alterations, permutations, and various substitute equivalents, whichfall within the scope of the disclosure. It will thus be appreciatedthat those skilled in the art will be able to devise numerous systemsand methods which, although not explicitly shown or described herein,embody the principles of the disclosure and are thus within the spiritand scope thereof.

ACRONYMS

-   HEVC: High Efficiency Video Coding-   HDR: high dynamic range-   SDR: standard dynamic range-   VVC: Versatile Video Coding-   JVET: Joint Video Exploration Team-   MPM: most probable mode-   WAIP: Wide-Angle Intra Prediction-   CU: Coding Unit-   PU: Prediction Unit-   PDPC: Position Dependent Prediction Combination-   ISP: Intra Sub-Partitions

1. A method of signaling an intra prediction mode used to encode acurrent block in an encoded video bitstream using at least oneprocessor, the method comprising: determining a plurality of candidateintra prediction modes; generating a most probable mode (MPM) list usingthe plurality of candidate intra prediction modes; signaling a referenceline index indicating a reference line used to encode the current blockfrom among a plurality of reference lines including an adjacentreference line and a plurality of non-adjacent reference lines; andsignaling an intra mode index indicating the intra prediction mode,wherein the MPM list is generated based on the reference line used toencode the current block and whether an intra sub-partition (ISP) modeis enabled, wherein the ISP mode relates to dividing lumaintra-predicted blocks vertically or horizontally into sub-partitionsbased on block size dimensions, wherein a first intra prediction mode ofthe MPM list is a planar mode.
 2. The method of claim 1, wherein a DCmode is included in the plurality of candidate intra prediction modes,wherein based on the reference line being the adjacent reference lineand the ISP mode being disabled, the MPM list includes all of theplurality of candidate intra prediction modes, and wherein based on thereference line being the adjacent reference line and the ISP mode beingenabled, the MPM list includes all of the plurality of candidate intraprediction modes except for the DC mode.
 3. The method of claim 1,wherein a DC mode is included in the plurality of candidate intraprediction modes, and wherein based on the reference line being theadjacent reference line and the ISP mode being enabled, the MPM listincludes all of the plurality of candidate intra prediction modes exceptfor the DC mode.
 4. The method of claim 1, wherein a DC mode and theplanar mode are included in the plurality of candidate intra predictionmodes, and wherein based on the reference line being the one from amongthe plurality of non-adjacent reference lines, the MPM list includes allof the plurality of candidate intra prediction modes except for the DCmode and the planar mode.
 5. The method of claim 1, wherein the MPM listis a same MPM list based on the reference line being the adjacentreference line and the ISP mode being disabled, based on the referenceline being the adjacent reference line and the ISP mode being enabled,and based on the reference line being the one from among the pluralityof non-adjacent reference lines.
 6. The method of claim 5, wherein asecond intra prediction mode of the MPM list is a DC mode.
 7. The methodof claim 1, wherein based on the reference line index indicating thatthe reference line is the adjacent reference line, a first one or twobins of the intra mode index are context coded, wherein a context isdetermined based on whether the ISP mode is enabled.
 8. The method ofclaim 1, wherein based on the reference line index indicating that thereference line is the adjacent reference line, a first one or two binsof the intra mode index are context coded, wherein a context isdetermined based on a value of the reference line index.
 9. The methodof claim 1, wherein based on the reference line index indicating thatthe reference line is the adjacent reference line, a first one or twobins of the intra mode index are context coded, wherein a context isdetermined based on whether the ISP mode is enabled and the referenceline index.
 10. The method of claim 1, wherein based on the referenceline index indicating that the reference line is the adjacent referenceline, a first two bins of the intra mode index are context coded,wherein a context is determined based on the intra mode index and areference line index indicating a reference line used to encode aneighboring block.
 11. A device for signaling an intra prediction modeused to encode a current block in an encoded video bitstream, the devicecomprising: at least one memory configured to store program code; and atleast one processor configured to read the program code and operate asinstructed by the program code, the program code including: determiningcode configured to cause the at least one processor to determine aplurality of candidate intra prediction modes; generating codeconfigured to cause the at least one processor to generate a mostprobable mode (MPM) list using the plurality of candidate intraprediction modes; first signaling code configured to cause the at leastone processor to signal a reference line index indicating a referenceline used to encode the current block from among a plurality ofreference lines including an adjacent reference line and a plurality ofnon-adjacent reference lines; and second signaling code configured tocause the at least one processor to signal an intra mode indexindicating the intra prediction mode, wherein the MPM list is generatedbased on the reference line used to encode the current block and whetheran intra sub-partition (ISP) mode is enabled, wherein the ISP moderelates to dividing luma intra-predicted blocks vertically orhorizontally into sub-partitions based on block size dimensions, whereina first intra prediction mode of the MPM list is a planar mode.
 12. Thedevice of claim 11, wherein based on the reference line being theadjacent reference line and the ISP mode being disabled, the MPM listincludes all of the plurality of candidate intra prediction modes. 13.The device of claim 11, wherein a DC mode is included in the pluralityof candidate intra prediction modes, and wherein based on the referenceline being the adjacent reference line and the ISP mode being enabled,the MPM list includes all of the plurality of candidate intra predictionmodes except for the DC mode.
 14. The device of claim 11, wherein a DCmode and the planar mode are included in the plurality of candidateintra prediction modes, and wherein based on the reference line beingthe one from among the plurality of non-adjacent reference lines, theMPM list includes all of the plurality of candidate intra predictionmodes except for the DC mode and the planar mode.
 15. The device ofclaim 11, wherein the MPM list is a same MPM list based on the referenceline being the adjacent reference line and the ISP mode being disabled,based on the reference line being the adjacent reference line and theISP mode being enabled, and based on the reference line being the onefrom among the plurality of non-adjacent reference lines.
 16. The deviceof claim 15, wherein a second intra prediction mode of the MPM list is aDC mode.
 17. The device of claim 11, wherein based on the reference lineindex indicating that the reference line is the adjacent reference line,a first one or two bins of the intra mode index are context coded,wherein a context is determined based on whether the ISP mode isenabled.
 18. The device of claim 11, wherein based on the reference lineindex indicating that the reference line is the adjacent reference line,a first one or two bins of the intra mode index are context coded,wherein a context is determined based on a value of the reference lineindex.
 19. The device of claim 11, wherein based on the reference lineindex indicating that the reference line is the adjacent reference line,a first one or two bins of the intra mode index are context coded,wherein a context is determined based on whether the ISP mode is enabledand the reference line index.
 20. A non-transitory computer-readablemedium storing instructions, the instructions comprising: one or moreinstructions that, when executed by one or more processors of a devicefor signaling an intra prediction mode used to encode a current block inan encoded video bitstream, cause the one or more processors to:determine a plurality of candidate intra prediction modes; generate amost probable mode (MPM) list using the plurality of candidate intraprediction modes; signal a reference line index indicating a referenceline used to encode the current block from among a plurality ofreference lines including an adjacent reference line and a plurality ofnon-adjacent reference lines; and signal an intra mode index indicatingthe intra prediction mode, wherein the MPM list is generated based onthe reference line used to encode the current block and whether an intrasub-partition (ISP) mode is enabled, wherein the ISP mode relates todividing luma intra-predicted blocks vertically or horizontally intosub-partitions based on block size dimensions, wherein a first intraprediction mode of the MPM list is a planar mode.